linux-kernel - Re: [PATCH tip:x86/mm 1/3] x86: A fast way to check capabilities of the current cpu

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Message-ID: <4D93531F.5080403@zytor.com>
Date:	Wed, 30 Mar 2011 08:58:23 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Tejun Heo <tj@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
	Christoph Lameter <cl@...ux.com>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>
Subject: Re: [PATCH tip:x86/mm 1/3] x86: A fast way to check capabilities
 of the current cpu

On 03/14/2011 12:49 PM, Andi Kleen wrote:
> Tejun Heo <tj@...nel.org> writes:
> 
>> Add this_cpu_has() which determines if the current cpu has a certain
>> ability using a segment prefix and a bit test operation.
> 
> 
> Hmm: if the CPU capability is really tested in a performance critical
> path, wouldn't it even be better to just use static_branch() now? 
> 

We have static_cpu_has() for this specific purpose (it actually predates
static_branch()).

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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